The present invention relates to an apparatus for and a method of inserting valves between front and back panels of inflatable bodies such as novelty balloons or dunnage bags. More particularly, this invention relates to a method and apparatus for inserting a valve between a front and back panel of an inflatable body without requiring that the valve be initially tacked or otherwise permanently attached and pre-positioned to one of the panels prior to conveying the panels through a die station which forms the completed inflatable body with a seal of all layers and the valve.
Currently, there are many types of inflatable bodies that are mass produced and easier methods for producing such inflatable bodies are useful in reducing the costs associated with such mass production. One example is novelty balloons of the metalized mylar or nylon type that typically have a front panel and back panel sealed together about their periphery to form an inflatable body. Such balloons often have novelty messages such as "Happy Birthday", "Happy Anniversary", "I Love You" and the like printed thereon and have become quite popular. Another example are inflatable dunnage bags that are a substitute for discrete packing materials and used for bearing against delicate or fragile articles in closed containers during shipment. Such inflatable dunnage bags are greatly advantageous over prior art methods, such as filling boxes full of styrofoam popcorn which can be harmful to the environment.
With respect to such novelty balloon and dunnage bag products, it is known to use an elongated, self-sealing valve comprised of top and bottom layers of flexible plastic film materials, which layers are sealed along their longitudinal edges to create a valve inlet, a valve outlet, and a passage therethrough. However, merely placing such self-sealing valves between the front and back panels of an inflatable body during the manufacturing, i.e., film conversion, process has proven to be disadvantageous. This is because if the valve is simply laid upon one of the webs of plastic film material that forms the top or bottom panel of the inflatable body, vibrations in the machinery, wind or air currents, gravity, and a variety of other factors can cause the valve to move relative to the web, thereby resulting in the valve being sealed between the body's panels in a misaligned fashion. Such products, when formed with such misaligned or otherwise improper valves, are non-usable and create wastage.
One method known in the art to prevent the above problems is to initially tack seal or otherwise permanently attach the valve to one of the panels or webs during the conversion process at a time prior to sealing the panels together to form the inflatable body. U.S. Pat. No. 4,917,646, issued to Kieves, is illustrative of such an initial tack sealing method. That patent discloses a valve that has a positioning tab which can be tacked with a heat seal, i.e., permanently pre-positioned, during the manufacturing process directly to one of the webs. Although tacking the valve to one of the panels will ensure that the valve is not misaligned or otherwise incorrectly placed in the inflatable body, the method is disadvantageous in that it requires the complicated, and additional, i.e., expensive, step of initially tack sealing the valve to one of the webs immediately after placement on the web to ensure that the valve does not become misaligned. This tack seal must be made before conveying the panels to a die station as such movement might cause the valve to become misaligned and such initial tack sealing and the equipment to perform it are cumbersome and expensive.
An important aspect of this invention therefore lies in providing a method and related apparatus for manufacturing an inflatable body with a self-sealing, flexible valve which does not require that the valve be initially tack sealed to or otherwise permanently pre-attached to one of the panels prior to conveying the film webs to a die station and forming the inflatable body from the panels. Briefly, the method of this invention comprises the steps of forming the self-sealing valve, conveying the upper web of sheet material through an upper roller assembly, and conveying a lower web of sheet material through a lower roller assembly. The next step is inserting the valve between the top and bottom webs at a position at which the webs are respectively passing through the roller assemblies and converging upon one another. Prior to insertion, the valve should be aligned perpendicular to the direction of travel of the webs. Thereafter, the next step is that the upper and lower roller assemblies are clamped together so as to bring the top and bottom webs together and frictionally engage the loosely inserted valve therebetween. The webs and frictionally clamped valve are then conveyed to a die station without any permanent pre-attachment of the valve to either of the webs. As a next step, at the die station the perimeter of an inflatable body shape is heat sealed onto the webs and the valve such that the valve is simultaneously heat sealed to both the webs, i.e., valve is sealed to both webs at the same time. Alternatively, an additional roller die can be provided just after the roller assemblies and before the die station to simultaneously heat seal the loosely inserted valve to both the top and bottom webs before the downstream heat sealing of the peripheral shape of the inflatable body.
In another embodiment of the method of this invention, where automation is desired, the method can additionally involve providing a linear slide having a distal end positioned adjacent to the upper and lower roller assemblies and a proximal end positioned a distance away from the roller assemblies. A guide rail is positioned parallel to the linear slide. A vacuum table is provided on the linear slide so as to be slideable between the distal and proximal ends of the linear slide. A separate valve forming apparatus, well known in the art, can then be located adjacent the linear slide and used to automatically form the valves and then place them on the vacuum table when the latter is positioned at the proximal end of the slide. Pneumatic vacuum ports are provided on the vacuum table to retain the valve inlet end of the valve in position on the table while the associated guide rail supports the outlet end of the valve. A further proximity sensor can be used to detect when a valve has been placed on the vacuum table, and the table can then be advanced to the distal end of the linear slide to insert the valve between the converging top and bottom webs. Thereafter, the steps of clamping the roller assemblies together about the film webs and loosely inserted valve, conveying the clamped webs and valve to a die station, and then heat sealing the peripheral shape of an inflatable body can all then be performed in a continuous, automatic operation.
The apparatus of this invention comprises an upper roller assembly, a lower roller assembly positioned adjacent to and below the upper roller assembly and means for conveying a top web through the upper roller assembly and a bottom web through the lower roller assembly. Valve insertion means are provided for inserting a valve between the top and bottom webs. Preferably, such a valve insertion means takes the form of a linear slide having a distal end positioned adjacent to the roller assemblies and a proximal end positioned a distance away from the roller assemblies, a guide rail positioned parallel to the length of the linear slide, and a vacuum table that is slideably mounted on said linear slide and is moveable between its distal and proximal ends. The vacuum table is further provided with vacuum ports for retaining a valve thereon. A valve may be placed on the vacuum table while it is at the proximal end of the linear slide and the vacuum table is slideable along the linear slide to the distal end at which point the vacuum table inserts the valve between the upper and lower webs. Thereafter, a die station is provided for heat sealing the perimeter of an inflatable body shape on the webs and simultaneously heat sealing the valve to both of the webs.
Preferably, the materials of which the valves and webs are comprised are selected based on their high instance of surface adhesion that occurs between the webs and the valve. Examples of such materials include constructing the webs of thin layers of high density polyethylene, low density polyethylene, linear low density polyethylene, and polypropylene or a combination of these materials, while constructing the valve of thin layers of high density polyethylene, low density polyethylene, linear low density polyethylene, and polypropylene or a combination of these materials. In one embodiment, the method involves the further steps of sensing with a proximity sensor when the valve is positioned between the top and bottom webs and then sending a signal to a pneumatic cylinder connected to the lower roller assembly, which is pivotally mounted to thereby perform the clamping step. In the situation where inflatable dunnage bags are being produced, for example, the valve can be inserted between the webs so that at least a portion of the valve, preferably at least 1 inch or more, extends out from between the periferally sealed film webs making up the bag body.
Other objects, features, and advantages of the present invention will become apparent from the following specification and drawings.